1/*
2  Copyright (c) 1990-2000 Info-ZIP.  All rights reserved.
3
4  See the accompanying file LICENSE, version 2000-Apr-09 or later
5  (the contents of which are also included in zip.h) for terms of use.
6  If, for some reason, all these files are missing, the Info-ZIP license
7  also may be found at:  ftp://ftp.info-zip.org/pub/infozip/license.html
8*/
9/* crctab.c -- supply the CRC table needed for CRC-32 calculations.
10 * Copyright (C) 1995 Mark Adler
11 * For conditions of distribution and use, see copyright notice in zlib.h
12 */
13
14/* $Id: crctab.c 1101 2002-09-21 14:54:45Z darkwyrm $ */
15
16/*
17  Generate a table for a byte-wise 32-bit CRC calculation on the polynomial:
18  x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
19
20  Polynomials over GF(2) are represented in binary, one bit per coefficient,
21  with the lowest powers in the most significant bit.  Then adding polynomials
22  is just exclusive-or, and multiplying a polynomial by x is a right shift by
23  one.  If we call the above polynomial p, and represent a byte as the
24  polynomial q, also with the lowest power in the most significant bit (so the
25  byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
26  where a mod b means the remainder after dividing a by b.
27
28  This calculation is done using the shift-register method of multiplying and
29  taking the remainder.  The register is initialized to zero, and for each
30  incoming bit, x^32 is added mod p to the register if the bit is a one (where
31  x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
32  x (which is shifting right by one and adding x^32 mod p if the bit shifted
33  out is a one).  We start with the highest power (least significant bit) of
34  q and repeat for all eight bits of q.
35
36  The table is simply the CRC of all possible eight bit values.  This is all
37  the information needed to generate CRC's on data a byte at a time for all
38  combinations of CRC register values and incoming bytes.
39*/
40
41#define __CRCTAB_C      /* identifies this source module */
42
43#include "zip.h"
44
45#if (!defined(USE_ZLIB) || defined(USE_OWN_CRCTAB))
46
47#ifndef ZCONST
48#  define ZCONST const
49#endif
50
51#ifdef DYNAMIC_CRC_TABLE
52
53/* =========================================================================
54 * Make the crc table. This function is needed only if you want to compute
55 * the table dynamically.
56 */
57
58local void make_crc_table OF((void));
59
60#if (defined(DYNALLOC_CRCTAB) && defined(REENTRANT))
61   error: Dynamic allocation of CRC table not safe with reentrant code.
62#endif /* DYNALLOC_CRCTAB && REENTRANT */
63
64#ifdef DYNALLOC_CRCTAB
65   local ulg near *crc_table = NULL;
66# if 0          /* not used, since sizeof("near *") <= sizeof(int) */
67   /* Use this section when access to a "local int" is faster than access to
68      a "local pointer" (e.g.: i86 16bit code with far pointers). */
69   local int crc_table_empty = 1;
70#  define CRC_TABLE_IS_EMPTY    (crc_table_empty != 0)
71#  define MARK_CRCTAB_FILLED    crc_table_empty = 0
72#  define MARK_CRCTAB_EMPTY     crc_table_empty = 1
73# else
74   /* Use this section on systems where the size of pointers and ints is
75      equal (e.g.: all 32bit systems). */
76#  define CRC_TABLE_IS_EMPTY    (crc_table == NULL)
77#  define MARK_CRCTAB_FILLED    crc_table = crctab_p
78#  define MARK_CRCTAB_EMPTY     crc_table = NULL
79# endif
80#else /* !DYNALLOC_CRCTAB */
81   local ulg near crc_table[256];
82   local int crc_table_empty = 1;
83#  define CRC_TABLE_IS_EMPTY    (crc_table_empty != 0)
84#  define MARK_CRCTAB_FILLED    crc_table_empty = 0
85#endif /* ?DYNALLOC_CRCTAB */
86
87
88local void make_crc_table()
89{
90  ulg c;                /* crc shift register */
91  int n;                /* counter for all possible eight bit values */
92  int k;                /* byte being shifted into crc apparatus */
93#ifdef DYNALLOC_CRCTAB
94  ulg near *crctab_p;   /* temporary pointer to allocated crc_table area */
95#else /* !DYNALLOC_CRCTAB */
96# define crctab_p crc_table
97#endif /* DYNALLOC_CRCTAB */
98
99#ifdef COMPUTE_XOR_PATTERN
100  /* This piece of code has been left here to explain how the XOR pattern
101   * used in the creation of the crc_table values can be recomputed.
102   * For production versions of this function, it is more efficient to
103   * supply the resultant pattern at compile time.
104   */
105  ulg xor;              /* polynomial exclusive-or pattern */
106  /* terms of polynomial defining this crc (except x^32): */
107  static uch p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
108
109  /* make exclusive-or pattern from polynomial (0xedb88320L) */
110  xor = 0L;
111  for (i = 0; i < sizeof(p)/sizeof(uch); i++)
112    xor |= 1L << (31 - p[i]);
113#else
114# define xor 0xedb88320L
115#endif
116
117#ifdef DYNALLOC_CRCTAB
118  crctab_p = (ulg near *) nearmalloc (256*sizeof(ulg));
119  if (crctab_p == NULL) {
120    ziperr(ZE_MEM, "crc_table allocation");
121  }
122#endif /* DYNALLOC_CRCTAB */
123
124  for (n = 0; n < 256; n++) {
125    c = (ulg)n;
126    for (k = 8; k; k--)
127      c = c & 1 ? xor ^ (c >> 1) : c >> 1;
128    crctab_p[n] = c;
129  }
130  MARK_CRCTAB_FILLED;
131}
132
133#else /* !DYNAMIC_CRC_TABLE */
134
135#ifdef DYNALLOC_CRCTAB
136   error: Inconsistent flags, DYNALLOC_CRCTAB without DYNAMIC_CRC_TABLE.
137#endif
138
139/* ========================================================================
140 * Table of CRC-32's of all single-byte values (made by make_crc_table)
141 */
142local ZCONST ulg near crc_table[256] = {
143  0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
144  0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
145  0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
146  0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
147  0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
148  0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
149  0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
150  0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
151  0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
152  0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
153  0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
154  0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
155  0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
156  0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
157  0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
158  0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
159  0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
160  0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
161  0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
162  0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
163  0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
164  0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
165  0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
166  0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
167  0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
168  0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
169  0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
170  0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
171  0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
172  0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
173  0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
174  0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
175  0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
176  0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
177  0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
178  0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
179  0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
180  0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
181  0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
182  0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
183  0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
184  0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
185  0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
186  0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
187  0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
188  0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
189  0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
190  0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
191  0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
192  0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
193  0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
194  0x2d02ef8dL
195};
196#endif /* ?DYNAMIC_CRC_TABLE */
197
198/* use "OF((void))" here to work around a Borland TC++ 1.0 problem */
199#ifdef USE_ZLIB
200ZCONST uLongf *get_crc_table OF((void))
201#else
202ZCONST ulg near *get_crc_table OF((void))
203#endif
204{
205#ifdef DYNAMIC_CRC_TABLE
206  if (CRC_TABLE_IS_EMPTY)
207    make_crc_table();
208#endif
209#ifdef USE_ZLIB
210  return (ZCONST uLongf *)crc_table;
211#else
212  return (ZCONST ulg near *)crc_table;
213#endif
214}
215
216#ifdef DYNALLOC_CRCTAB
217void free_crc_table()
218{
219  if (!CRC_TABLE_IS_EMPTY)
220  {
221    nearfree((ulg near *)crc_table);
222    MARK_CRCTAB_EMPTY;
223  }
224}
225#endif
226
227#endif /* !USE_ZLIB || USE_OWN_CRCTAB */
228